Conventionally, as an impact torque generating device of a torque wrench, a hydraulic torque wrench utilizing a hydraulic impact torque generating device small in noise and vibration has been developed and put in use (see, for example, patent literature 1 and 2).
FIG. 7 and FIG. 8 show an example of this hydraulic torque wrench, in which a hydraulic torque wrench 1 includes a main valve 2 for supplying and stopping high-pressure air, and a normal and reverse rotation changeover valve 3 for selectively generating impact torques in normal and reverse rotations. A rotor 4 for generating a rotational torque is driven by the air-pressure air sent through the both valves 2, 3. A hydraulic impact torque generating device 5 for converting the rotational torque of the rotor 4 to an impact torque is provided in a case 6 of the hydraulic torque wrench 1.
In the hydraulic impact torque generating device 5, a hollow space formed in a liner 7 rotated by the rotor 4 is filled and sealed with a working fluid, two blade insertion grooves (or one or three or more) are provided in a main shaft 8 inserted coaxially in the liner 7, blades 9 are inserted in the blade insertion grooves, and the blades 9 are always biased in the outer circumferential direction of the main shaft 8 so as to contact with the inner circumference of the liner 7 by spring 10.
The impact torque generating device 5 is also provided with an output adjusting mechanism 11 for adjusting the magnitude of the generated impact torque.
By rotating and driving the liner 7 by the rotor 4, when a plurality of seal surfaces formed on the inner circumference of the liner 7, seal surfaces formed on the outer circumference of the main shaft 8, and the blades 9 are matched, an impact torque is generated in the main shaft 8, and then nuts and other parts engaged with the leading end of the main shaft 8 are tightened or loosened.
In the conventional hydraulic torque wrench, the output adjusting mechanism 11 for adjusting the magnitude of the impact torque is designed to adjust the size of the working fluid path communicating with the inside of the liner 7 composed of a high-pressure chamber and a low-pressure chamber at the time of generation of the impact torque by manipulating an operation shaft. More specifically, when the operation shaft is manipulated to a releasing side to increase the working fluid path, the impact torque decreases, and to the contrary when the operation shaft is manipulated to a closing side to decrease the working fluid path, the impact torque increases.
However, the size of the working fluid path adjusted by manipulation of the operation shaft had the following problems (1) to (4) because it is the same (fixed) during operation of the hydraulic torque wrench.
(1) There is a large difference between the magnitude of the impact torque actually generated and the preset impact torque.
(2) An abnormally high impact torque is likely to be generated upon start of a tightening operation (at the time of seating of a tightening member).
(3) The resistance is large after generation of impact torque (after pulse generation), and the generation period of impact torques is long.
(4) A loading torque is likely to be applied to the seal part, and the durability is poor.
To solve these problems, the present applicant previously proposed an impact torque adjusting device of a hydraulic torque wrench capable of enhancing the precision of the magnitude of the impact torque generated by the impact torque generating device of the hydraulic torque wrench, shortening the generation period of impact toques, and enhancing the durability of the impact torque generating device of the hydraulic torque wrench (see, for example, patent literature 3).
FIG. 2 and FIG. 3 show a first reference example of an impact torque generating device of a hydraulic torque wrench.
A hydraulic torque wrench 1 of this reference example has a magnetorestrictive torque detection mechanism 12 same as the conventional hydraulic torque wrench disclosed in patent literature 2, and by the output of this magnetorestrictive torque detection mechanism 12, driving of a rotor 4 and others is controlled. It further includes a main valve 2 for supplying and stopping high-pressure air, and a normal and reverse rotation changeover valve 3 for selectively generating impact torques in normal and reverse rotations. The rotor 4 for generating a rotational torque is driven by the air-pressure air sent through both valves 2, 3, and a hydraulic impact torque generating device 5 for converting the rotational torque of the rotor 4 to an impact torque is provided in a case 6 of the hydraulic torque wrench 1.
In the hydraulic impact torque generating device 5, a hollow space formed in a liner 7 rotated by the rotor 4 is filled and sealed with a working fluid, two blade insertion grooves (or one or three or more) are provided in a main shaft 8 inserted coaxially in the liner 7, blades 9 are inserted in the blade insertion grooves, and the blades 9 are always biased in the outer circumferential direction of the main shaft 8 so as to contact with the inner circumference of the liner 7 by spring 10.
The impact torque generating device 5 is also provided with an output adjusting mechanism 11 for adjusting the magnitude of the generated impact torque.
By rotating and driving the liner 7 by the rotor 4, when a plurality of seal surfaces formed on the inner circumference of the liner 7, seal surfaces formed on the outer circumference of three main shaft 8, and the blades 9 are matched, an impact torque is generated in the main shaft 8, and nuts and other parts engaged with the leading end of the main shaft 8 are tightened or loosened.
In the hydraulic torque wrench of this reference example, the output adjusting mechanism 11, by manipulating an operation shaft 11a, is designed to adjust the size of a working fluid path 11b communicating with the inside of the liner 7 composed of a high-pressure chamber H and a low-pressure chamber L at the time of generation of a impact torque (more specifically, when the operation shaft 11a is manipulated to a releasing side to increase the working fluid path 11b (not to narrow), the impact torque decreases, and to the contrary when the operation shaft 11a is manipulated to a closing side to decrease the working fluid path 11b (to narrow), the impact torque increases).
Further, this output adjusting mechanism 11 is provided with a valve body 11d disposed in the working fluid path 11b so as to be formed in a direction of releasing the working fluid path 11b by way of the operation shaft 11a and a spring 11c, and the rear back side of this valve body 11d is provided with an oil chamber 11e communicating with the inside of the liner 7 which is the high-pressure chamber H at the time of generation of an impact torque. When the pressure of the working fluid in the high-pressure chamber H elevates along with the progress of the tightening operation, the working fluid path 11b is decreased (narrowed) as shown in FIG. 3 (a) to FIG. 3 (b), along with elevation of pressure of the working fluid in this high-pressure chamber H.
As a result, it is capable of enhancing the precision of the magnitude of the impact torque generated by the impact torque generating device of the hydraulic torque wrench, shortening the generation period of impact toques, and enhancing the durability of the impact torque generating device of the hydraulic torque wrench.
The above action and effects are explained as follows by referring to the output characteristic diagrams in FIG. 4. FIG. 4 (a) shows prior art where the size of the working fluid path is constant (fixed while the hydraulic torque wrench is working, and FIG. 4 (b) showing the present reference example, respectively.
(1) Since it is possible to control accurately the pressure of the working fluid inside of the liner 7, becoming the high-pressure chamber H depending on the tightening state, it is possible to enhance the precision of the magnitude of the impact torque because the error between the magnitude of the impact torque actually generated and the preset impact torque is in a relation of prior art: Δt1>reference example: Δt2.
(2) Upon start of a tightening operation (at the time of seating of a tightening member), since the working fluid path 11b is wide (not narrowed), unlike the prior art, an abnormally high impact torque tx is not generated.
(3) After generation of impact torque (after pulse generation), since the working fluid path 11b is wide (not narrowed), the resistance is small after generation of impact torque (after pulse generation), and the generation period of impact pulses is in a relation of prior art: T1>reference example: T2, and the working time required for tightening can be shortened.
(4) Since it is possible to control accurately the pressure of the working fluid inside the liner 7, becoming the high-pressure chamber H depending on the tightening state, loading pressure is hardly applied to the seal part such as in the prior art, and it is possible to enhance the durability of the impact torque generating device 5.
FIG. 5 shows a second reference example of an impact torque adjusting device of a hydraulic torque wrench.
A hydraulic torque wrench 1 of this reference example, unlike the first reference example having the magnetorestrictive torque detection mechanism 12 or the like for controlling the rotor 4 and others by the output of the torque detection mechanism, is similar to the conventional hydraulic torque wrench disclosed in patent literature 1 and FIG. 8, in which a relief valve B is disposed in an output adjusting mechanism 11. When the pressure (impact torque) of the working fluid in the high-pressure chamber H reaches a predetermined magnitude as the tightening operation is advanced, the relief valve B is released, and the pressure of the working fluid is transmitted to a shut-off valve mechanism 13.
In the case of the hydraulic torque wrench 1 of this type, since the valve body 11d cannot be assembled in the output adjusting mechanism 11, a valve body 14d is assembled in the liner 7, aside from the output adjusting mechanism 11.
The valve body 14d is biased in a direction of releasing the working fluid path 14b by way of a spring 14c, and the rear back side of this valve body 14d is provided with an oil chamber 14e communicating with the inside of the liner 7, which is the high-pressure chamber H at the time of generation of an impact torque. When the pressure of the working fluid in the high-pressure chamber H elevates along with the progress of the tightening operation, the working fluid path 14b is decreased (narrowed) along with elevation of pressure of the working fluid in this high-pressure chamber H.
The action of the impact torque adjusting device of the hydraulic torque wrench of this reference example is the same as that of the impact torque adjusting device of the hydraulic torque wrench of the first reference example.
FIG. 6 shows a third reference example of an impact torque adjusting device of a hydraulic torque wrench.
A hydraulic torque wrench 1 of this reference example is similar to the second reference example, in which a relief valve is disposed in an output adjusting mechanism 11 (detail shown in FIG. 5). When the pressure (impact torque) of the working fluid in the high-pressure chamber H reaches a predetermined magnitude as the tightening operation is advanced, the relief valve is released, and the pressure of the working fluid is transmitted to a shut-off valve mechanism 13 (see FIG. 8).
In the case of the hydraulic torque wrench 1 of this type, since the valve body 11d cannot be assembled in the output adjusting mechanism 11, a valve body 15d is assembled in the liner 7, aside from the output adjusting mechanism 11.
The valve body is composed of two valve bodies 15d disposed oppositely to each other across the working fluid path 15b, and is biased in a direction of releasing the working fluid path 15b by way of the spring 15c. 
The rear back side of each valve body 15d is provided with an oil chamber 15e communicating with the inside of the liner 7, which is the high-pressure chamber H at the time of generation of an impact torque. When the pressure of the working fluid in the high-pressure chamber H elevates along with the progress of the tightening operation, the working fluid path 15b is decreased (narrowed) along with elevation of pressure of the working fluid in this high-pressure chamber H.
The action of the impact torque adjusting device of the hydraulic torque wrench of this reference example is the same as that of the impact torque adjusting device of the hydraulic torque wrench of the first and second reference examples, but the two valve bodies 15d are disposed oppositely to each other across the working fluid path 15b. Depending on the elevation of the pressure of the working fluid in the high-pressure chamber H, the two valve bodies 15d are moved to decrease (narrow) the working fluid path 15b, so that the moving stroke of the valve bodies 15d when moving for adjusting the size of the working fluid path 15b can be decreased, and the response performance is enhanced, and the precision of magnitude of the impact torque can be further enhanced.